CHLORMEQUAT CHLORIDE (CCC) PRETREATMENTS MAY ENHANCE QUACKGRASS (ELYTRIGIA-REPENS) CONTROL WITH SETHOXYDIM

Laboratory, greenhouse, and field experiments were conducted at the La combe Research Station to determine if CCC, ethephon, or CCC/ethephon had direct activity on quackgrass rhizome buds, and to determine if fo liar applications of CCC/ethephon could predispose quackgrass to more effective control with sethoxydim. CCC, ethephon, and CCC/ethephon had growth regulating effects on the axillary buds and the apex of detach ed quackgrass rhizomes. CCC increased rhizome bud sprouting on rhizome s with the apex excised, but not on rhizomes with an intact apex. Ethe phon or CCC/ethephon inhibited bud sprouting on rhizomes with an intac t or excised apex. CCC/ethephon, but not CCC or ethephon alone, increa sed rhizome elongation on rhizomes with intact apices. In the greenhou se, pretreatments of CCC/ethephon increased sethoxydim activity on qua ckgrass rhizome buds and caused lower shoot emergence from one-bud rhi zome segments. Results of field experiments were less consistent than those in the greenhouse. However, sometimes CCC or CCC/ethephon pretre atments resulted in increased quackgrass control in the field with set hoxydim. Nomenclature: Chlormequat chloride or CCC, (2-chloroethyl)tri methylammoniumchloride; ethephon, (2-chloroethyl)phosphonic acid; seth oxydim, mino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-?? cyclohexen- 1-one}; quackgrass, (Elytrigia repens (L.) Nevski) #3 AGRRE.